Currently Being ModeratedJan 17, 2013 8:12 AM (in response to Pembroke House)
I don't know of any free ones, but you can try PrintCentral ($9.99, I think). It's OK, but like all third party print utilities, it's kind of a Rube Goldberg solution. It's not integrated into the iOS the way AirPrint is. If you want to print something, you either have to use its built-in email and web-browser (which suck), or use yet another program, like DropBox, as a go-between.
For the record, in my case I consider it $9.99 wasted. I used it once to prove it worked and haven't touched it since. If I need to print something, it's usually easier to mail it to myself or save it to DropBox, then print it from the computer sitting next to my printer.